Basically high resilience polyurethane foams are produced by the reaction of highly primary hydroxylcapped, high molecular weight polyols with organic isocyanates and water. High resilience polyurethane foams are distinguishable, in part, from conventional hot cure polyurethane foams by the use of such polyols and the fact that high resilience polyurethane foams require little or no oven curing and thus are often referred to as cold cure foams. Such foams are extremely desirable for cushioning applications because of their excellent physical properties, e.g., very high foam resilience, low flammability, opencelled structure, low flex fatigue (long life) and high SAC factors (load bearing properties).
Because of the high reactivity of high resilience foam ingredients and their rapid buildup of gel strength, sometimes the foam can be obtained without a cell stabilizer. However, such foams typically have very irregular cell structure as particularly evidenced by surface voids and the lack of discovery of a proper agent to help control cell structure has been a major problem in the art.
Attempts to solve this problem with surfactants generally employed in the stabilization of hot cure polyurethane foam have not proven satisfactory because such surfactants tend to overstabilize, causing extremely tight, shrinking forms. Nor is the problem corrected by reducing the concentrations of such surfactants, since at concentrations required to eliminate shrinkage, the cells are no longer stabilized satisfactorily and the foam structure becomes irregular, coarse and contains surface voids.
U.S. Pat. No. 4,119,582 discloses a process for manufacturing high resilience flexible polyurethane foam using as a foam stabilizer a mixture of a "high" molecular weight siloxane-oxyalkylene copolymer with a "low" molecular weight siloxane-oxyalkylene copolymer. The "high" molecular weight siloxane-oxyalkylene copolymer contains at least five oxyalkylene units in each oxyalkylene block and is present in the mixture in an amount of from 84.0 to 99.8 weight percent and the "low" molecular weight siloxane-oxyalkylene copolymer contains up to four oxyalkylene units in each oxyalkylene block and is present in the mixture in an amount of from 0.2 to 16.0 weight percent. The "high" molecular weight siloxane-oxyalkylene copolymer has a molecular weight range of from 1,000 to 16,000 and the "low" molecular weight siloxane-oxyalkylene copolymer has a molecular weight range of from 500 to 10,000. Hence, the two classes of copolymers are not necessarily distinguished by their molecular weights but rather by the number of oxyalkylene units in the oxyalkylene blocks. This patent discloses that humidity resistance is the principal foam property improved by the use of the copolymer mixtures. The only foams exemplified are apparently of moderate density (i.e., they are apparently produced from reaction mixtures containing 2.7 parts by weight water per 100 parts by weight of polyol). The only exemplified copolymer mixture whose specific composition is given comprises "Surfactant A" whose calculated molecular weight is 5946 and "Surfactant B" whose calculated molecular weight is 1716.
Several other patents disclose organosiloxane copolymers and their use as foam stabilizers in high resilience foam formulations. U.S. Pat. No. 4,042,540 discloses that a variety of low viscosity siloxanes (e.g., low viscosity alkoxy-modified siloxanes and low viscosity dimethylsilicone oils) are better stabilizers for high resilience polyurethane foams than higher viscosity dimethylsilicone oils. U.S. Pat. No. 3,905,924 relates to the use of cyanoalkylsiloxanes and mixtures of such siloxanes as stabilizers for high resilience polyurethane foam while U.S. Pat. No. 3,839,384 discloses that use for aralkylsiloxanes. U.S. Pat. No. 3,741,917 describes siloxane-oxyalkylene copolymers and mixtures thereof with each other or with dimethylsilicone oils (only the copolymer-oil mixtures are exemplified). The latter patent also discloses the use of said copolymers and mixtures in the formulation of high resilience polyurethane foam. U.S. Pat. No. 3,935,133 teaches the use of high molecular weight silicate esters of polyether alcohols to stabilize high resilience polyurethane foam. U.S. Pat. No. 4,210,726 discloses a process for producing high resilience polyurethane foam utilizing as a foam stabilizer a combination of an organosiloxane copolymer and a hydrocarbon oil. U.S. patent application Ser. No. 134,637, filed Mar. 27, 1980, describes organosiloxane copolymers containing alkyl groups having from 5 to 20 carbon atoms that have beneficial utility as foam stabilizers in the manufacture of low density high resilience polyurethane foam. U.S. patent application Ser. No. 154,849 filed May 30, 1980, describes a process for manufacturing low density high resilience polyurethane foams utilizing as a foam stabilizer selected low molecular weight alkoxysilicone compositions containing from one to 18 silicon atoms in which the alkoxy-modifying group contains from 5 to 18 carbon atoms. However, none of the above mentioned patents or applications disclose the novel siloxane copolymer mixtures of this invention or their unexpectedly beneficial utility as foam stabilizers in the manufacture of low density high resilience polyurethane foam.
Within the past few years, cushions fabricated from high resilience polyurethane foam have gained increasingly wide acceptance in automotive seatings. Automotive industry requirements decreased the foam density needed for seat cushions, thus increasing the difficulty of stabilization of high resilience polyurethane foam. Recently new polymer/polyol systems with high water levels have been proposed which can produce foam cushions with densities of 1.50 to 1.75 lbs./cubic foot and acceptable physical properties in comparison to the commercial foaming systems. However, without any foam stabilizing surfactant, the new polymer/polyol-high water systems produced foams with large and irregular cells or caused collapse of the foam. The addition of commercial high resilience polyurethane foam surfactants (including the low viscosity dimethylsilicone oils, cyanoalkylsiloxanes and siloxane-oxyalkylene copolymers disclosed in the above-mentioned patents) to this new polymer/polyol-high water system did not correct these problems. The commercial high resilience polyurethane foam surfactants caused collapse of the foams, and commercial flexible "hot-cure" polyurethane surfactants caused severe shrinkage and pneumatic foams. Thus, it is a problem in low density high resilience polyurethane foam formulations to obtain a surfactant which has a proper degree of cell stabilizing ability. This problem is solved by the present invention and also by copending U.S. application Ser. No. 134,637, filed Mar. 27, 1980, and copending U.S. application Ser. No. 154,849 filed May 30, 1980, described hereinabove.